I wrote a little function that will solve the loading problem cross-browser including FF. The comments on GitHub help explain usage. Full code at https://github.com/srolfe26/getXDomainCSS.
Disclaimer: The code below is jQuery dependent.
Sometimes, if you're pulling CSS from a place that you can't control the CORS settings you cans till get the CSS with an <link> tag, the main issue to be solved then becomes knowing when your called-for CSS has been loaded and ready to use. In older IE, you could have an on_load listener run when the CSS is loaded.
Newer browsers seem to require old-fashioned polling to determine when the file is loaded, and have some cross-browser issues in determining when the load is satisfied. See the code below to catch some of those quirks.
/**
* Retrieves CSS files from a cross-domain source via javascript. Provides a jQuery implemented
* promise object that can be used for callbacks for when the CSS is actually completely loaded.
* The 'onload' function works for IE, while the 'style/cssRules' version works everywhere else
* and accounts for differences per-browser.
*
* @param {String} url The url/uri for the CSS file to request
*
* @returns {Object} A jQuery Deferred object that can be used for
*/
function getXDomainCSS(url) {
var link,
style,
interval,
timeout = 60000, // 1 minute seems like a good timeout
counter = 0, // Used to compare try time against timeout
step = 30, // Amount of wait time on each load check
docStyles = document.styleSheets // local reference
ssCount = docStyles.length, // Initial stylesheet count
promise = $.Deferred();
// IE 8 & 9 it is best to use 'onload'. style[0].sheet.cssRules has problems.
if (navigator.appVersion.indexOf("MSIE") != -1) {
link = document.createElement('link');
link.type = "text/css";
link.rel = "stylesheet";
link.href = url;
link.onload = function () {
promise.resolve();
}
document.getElementsByTagName('head')[0].appendChild(link);
}
// Support for FF, Chrome, Safari, and Opera
else {
style = $('<style>')
.text('@import "' + url + '"')
.attr({
// Adding this attribute allows the file to still be identified as an external
// resource in developer tools.
'data-uri': url
})
.appendTo('body');
// This setInterval will detect when style rules for our stylesheet have loaded.
interval = setInterval(function() {
try {
// This will fail in Firefox (and kick us to the catch statement) if there are no
// style rules.
style[0].sheet.cssRules;
// The above statement will succeed in Chrome even if the file isn't loaded yet
// but Chrome won't increment the styleSheet length until the file is loaded.
if(ssCount === docStyles.length) {
throw(url + ' not loaded yet');
}
else {
var loaded = false,
href,
n;
// If there are multiple files being loaded at once, we need to make sure that
// the new file is this file
for (n = docStyles.length - 1; n >= 0; n--) {
href = docStyles[n].cssRules[0].href;
if (typeof href != 'undefined' && href === url) {
// If there is an HTTP error there is no way to consistently
// know it and handle it. The file is considered 'loaded', but
// the console should will the HTTP error.
loaded = true;
break;
}
}
if (loaded === false) {
throw(url + ' not loaded yet');
}
}
// If an error wasn't thrown by this point in execution, the stylesheet is loaded, proceed.
promise.resolve();
clearInterval(interval);
} catch (e) {
counter += step;
if (counter > timeout) {
// Time out so that the interval doesn't run indefinitely.
clearInterval(interval);
promise.reject();
}
}
}, step);
}
return promise;
}
